UICollectionView fed by NSFetchedResultsController

GridTableViewController.m

#pragma mark - NSFetchedResultsControllerDelegate

- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
    self.pendingObjectUpdates = [NSMutableArray array];
    self.pendingSectionUpdates = [NSMutableArray array];
}

- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
           atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {
    
    __weak UICollectionView *collectionView = self.collectionView;
    CollectionViewUpdateBlock updateBlock;
    
    switch(type) {
        case NSFetchedResultsChangeInsert:
        {
            updateBlock = ^(){[collectionView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex]];};
            break;
        }
        case NSFetchedResultsChangeDelete:
        {
            updateBlock = ^(){[collectionView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex]];};
            break;
        }
        case NSFetchedResultsChangeMove:break;
        case NSFetchedResultsChangeUpdate:break;
    }
    [self.pendingSectionUpdates addObject:updateBlock];
}

- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
       atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
      newIndexPath:(NSIndexPath *)newIndexPath {
    
    __weak UICollectionView *collectionView = self.collectionView;
    CollectionViewUpdateBlock updateBlock;
    
    switch(type) {
            
        case NSFetchedResultsChangeInsert:
        {

            updateBlock = ^{DLog(@"processing insert to %@",newIndexPath); [collectionView insertItemsAtIndexPaths:@[newIndexPath]];};
            break;
        }
        case NSFetchedResultsChangeDelete:
        {
            updateBlock = ^{DLog(@"processing delete to %@",indexPath); [collectionView deleteItemsAtIndexPaths:@[indexPath]];};
            break;
        }
        case NSFetchedResultsChangeUpdate:
        {
            updateBlock = ^{DLog(@"processing update to %@",indexPath);[self configureCell:(HLGridTableCell*)[collectionView cellForItemAtIndexPath:indexPath] atIndexPath:indexPath];};
            break;
        }
        case NSFetchedResultsChangeMove:
        {
            updateBlock = ^{DLog(@"processing move from %@ to %@",indexPath,newIndexPath); [collectionView moveItemAtIndexPath:indexPath toIndexPath:newIndexPath];};
            break;
        }
    }
    [self.pendingObjectUpdates addObject:updateBlock];
}

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
    if ([self.pendingSectionUpdates count])
    {
        [self.collectionView performBatchUpdates:^{
            for (CollectionViewUpdateBlock updateBlock in self.pendingSectionUpdates)
            {
                updateBlock();
            }
        } completion:nil];
    }
    
    if ([self.pendingObjectUpdates count] > 0 && [self.pendingSectionUpdates count] == 0)
    {
        [self.collectionView performBatchUpdates:^{
            for (CollectionViewUpdateBlock updateBlock in self.pendingObjectUpdates)
                updateBlock();
        } completion:nil];
    }
    self.pendingSectionUpdates = nil;
    self.pendingObjectUpdates = nil;
}